A three-way agreement between lender, landlord, and tenant that sets what happens to a lease if the lender forecloses. A standard closing requirement on tenanted commercial property.
The longer version
An SNDA does three jobs in one document. Subordination places the tenant's lease behind the lender's mortgage in priority. Non-disturbance is the lender's promise that a paying tenant keeps their lease even through foreclosure. Attornment is the tenant's promise to recognize whoever ends up owning the building as their new landlord.
Lenders require SNDAs from major tenants because they protect the collateral's income through a default scenario. Tenants negotiate them because non-disturbance is their protection against losing the space they operate in.
Like estoppels, SNDAs are third-party paper: they route through tenants and their counsel on their own schedule, which is why they belong on a tracked checklist early, not in a final-week scramble.
In Prodeal
SNDAs sit on the closing checklist with per-item ownership and due dates, and outside counsel can be given access scoped to exactly the documents they need to review.